Conventional clay bentonitic-type mud systems have inherent limitations that require the use of various drilling additives to control flow properties when the fluid encounters conditions in drilling operations which might detrimentally alter mud properties. These changes result in lower drilling and penetration rates and delays in drilling operations, which, in turn, increase overall drilling costs. In many cases with conventional drilling fluids, such additives only create more problems. This is due to the fact that while serving to control a specific mud property the additive may produce additional undesirable effects on the mud system. This may result from the additive being imcompatible with other components in the system, or may be due to a direct effect on mud properties. Also, such drilling fluids are adversely affected when they become contaminated with calcium compounds, potassium or sodium chlorides, etc. Thus, with high salt or calcium contamination, the effect on yield point, gel strengths, and fluid loss characteristics of such conventional muds renders the latter essentially useless unless special treatment procedures are employed. When anticipated calcium concentrations in excess of 200 ppm are predicted for a non-dispersed (bentonitic-extended polymer mud) drilling fluid, soda ash (Na.sub.2 CO.sub.3), is usually recommended as a treatment to eliminate calcium. Otherwise, the calcium will react with the montmorillonite converting the clay to a calcium montmorillonite which usually results in a flocculation of clay particles and a very high fluid loss. In the case of high salt contamination, bentonite muds are usually not run. Instead, salt gel or attapulgite is used as a viscosifier. Even in the case of a prehydrated bentonite which is suddenly contaminated with salt, serious detrimental effects on flow properties result. This is particularly true in the case of highly dispersed muds. For example, the plastic viscosity decreases, the fluid loss increases, and the gel strengths increase.
Hydration of gumbo and similar shales, when drilling with water-based fluids, can become particularly troublesome. This is primarily for the reason that on contact with a water-based mud, gumbo shale tends to swell and slough into the well, often resulting in stuck pipe, and in some cases abandonment of the well itself. Frequently, oil-based or invert emulsion muds are used to control hydration of shales. These drilling fluids are expensive. Moreover, in many areas the drilled solids must be cleaned before disposal.